Typically, the conventional voltage regulator circuit includes an operational amplifier (OP Amp) and a power metal-oxide semiconductor field-effect transistor (MOSFET). Specifically, the power MOSFET is configured to have its one source/drain terminal providing an output voltage; and the operational amplifier is configured to control the conduction degree of the power MOSFET according to the value of the output voltage.
However, due to requiring operating the operational amplifier at saturation, the conventional voltage regulator circuit, cannot be operated at low voltages.